Someone in my neighborhood wants to donate a used Aron Kodesh to a shul. There is a shul in my neighborhood that I thought could use it, but they have one, already. But, I'm wondering if they would be allowed to use it as a Sefarim closet? Or is this a case (no pun, intended) of moridin bakodesh (descending in holiness)?
I checked Talmud Megillah 26b which lists tashmishei kodesh and tashmishei mitzvah. They mention תיק של ס"ת, which I don't think is the same as an Aron. So, I'm uncertain what category that would be considered.